We propose to study the interaction of naturally occurring steroids with Neisseria gonorrhoeae and how this interaction influences the growth of the organism, its virulence, and the effectiveness of therapeutic agents. These studies will investigate the inhibition of membrane-associated and cytoplasmic activities by steroids using uptake of labeled substrates by membrane vesicles, leakage of cellular constituents, inhibition of glucose-6-phosphate dehydrogenase (and other enzymes), and alteration of glucose metabolism as measured by radiorespirometry and cell fractionation studies. We will also study the role of the outer membrane in this interaction by ascertaining the ability of steroids to inhibit the growth of organisms known to, or thought to, have an altered outer membrane. In addition, we will investigate the binding of labeled steroids to purified outer membranes as well as determine the chemical nature and specificity of the binding sites. Similar studies concerning the chemical nature and specificity of inner membrane binding sites will also be performed. Since the ability to inhibit the growth of N. gonorrhoeae is not a general property of all steroids, we propose to study the relationship between steroid structure and its binding ability. If binding does occur, we will determine the site and nature of these binding sites. Not all steroid-gonococcal interactions may be harmful. We propose to study the interaction of serum proteins and steroids with N. gonorrhoeae to determine whether the organism's response to killing by antibodies and complement or its sensitivity to antibiotics has been altered. We further plan to investigate whether steroids alter the virulence of N. gonorrhoeae in a chicken embryo model. BIBLIOGRAPHIC REFERENCES: Miller, R. D. and S. A. Morse. 1977. Binding of steroids to Neisseria gonorrhoeae. Infect. Immun. 15, in press. Morse, S. A., L. Bartenstein, and W. S. Wegener, 1977. Absence of 3',5'-cyclic adenosine monophosphate in Neisseria gonorrhoeae. Proc. Soc. Exp. Biol. Med. 155, in press.